The present invention relates to a motor having a dynamic pressure bearing and a rotator device having a rotator which is driven by the motor.
In the typical motor having a dynamic pressure bearing and the typical rotator device having a rotator which is driven by the motor, metal material such as aluminum alloy, ceramic material, and two kinds of metal material and ceramic material are used for the dynamic pressure bearing. Although there are a radial dynamic pressure bearing and a thrust dynamic bearing in the dynamic pressure bearing, they are usually adopted at the same time. There are many rotator devices in which rotator thereof is driven by the which conventional bearing. An example is described in Japanese Opened Patent No. 63-241516. As shown in FIG. 2, the rotator device disclosed in the Japanese patent is a polygon mirror device having a polygon rotor in which a rotator 3 having mirror surface 2 is rotatably formed at a fixed shaft 5 formed at a supporting body 4, wherein said rotator 3, the supporting body 4, and the fixed shaft 5 fixed at the supporting body 4 are made of ceramic material, and grooves 11 for generating dynamic pressure are formed at any sliding surface formed facing said supporting body 4 and/or fixed shaft 5.
The grooves for generating dynamic pressure include a groove for generating radial dynamic pressure and a groove for generating thrust dynamic pressure: the former is a herringbone groove G1 formed at either of inner circumferential surface of a penetration hole in the rotator 3 through which the fixed shaft 5 is inserted or the outer circumferential surface of the fixed shaft 5, as shown in FIG. 3; and the latter is a spiral groove G2 formed at either of the lower surface of the rotator 3 and the lower surface of the supporting body 4 facing under surface of the rotor. Although the groove for generating dynamic pressure is formed at dynamic pressure bearing member of ceramic material using shot blast, the processing is not easy. Using NC processing or deformation processing by ball form rolling, Herringbone groove and spiral groove are usually processed at dynamic pressure bearing member of soft metal such as copper alloy or aluminum alloy. These processes too are not easy and involving significant time and labor.
An object of the present invention is to provide a dynamic pressure bearing having a structure in which a groove for generating dynamic pressure is worked easy in the motor having dynamic pressure hearing and the rotator device having the motor as a driving source.